Rotary vane machine with fluid flow paths on each vane side

ABSTRACT

A hydraulic vane motor having rotor vanes radially displaceable in slots, in which a pressure chamber is disposed in the inner part of each slot. The outer edge of a vane is pressed against a work portion of a cam profile by fluid pressure acting on the bottom of the vane. Radially directed flow paths along the broad sides of each vane, plus a small circumferential movement of the vane in the slot, provide different flow resistances on the opposite sides of the vane.

United States Patent Ekenberg et al.

[4 1 Sept. 23, 1975 ROTARY VANE MACHINE WITH FLUID FLOW PATHS ON EACHVANE SIDE Inventors: Ulf Christer Ekenberg; Johan Paul Strom; RagnarGeorg Jonsson, all of Jakobsberg, Sweden Assignee: U.S. PhilipsCorporation, New

York, NY.

Filed: Sept. 9, 1974 Appl. No.: 504,534

Related US. Application Data Continuation of Ser. No. 305,297, Nov. 10,1972, abandoned.

Foreign Application Priority Data Nov. 12, 1971 Sweden 14491/71 US. Cl418/82; 418/268 Int. C1. F01C l/00; F03C 3/00; F04C 1/00;

FOlC 21/00 Field of Search 418/267, 268, 82, 184

References Cited UNITED STATES PATENTS 3/1945 Tucker et a1. 418/2682,435,279 2/1948 Hubucker 418/268 3,076,415 2/1963 Farron 418/2683,086,475 4/1963 Rosaen 418/268 3,609,071 9/1971 Brown 418/267 3,627,45612/1971 Gerlach 418/268 Primary Examiner-John J. Vrablik Attorney,Agent, or FirmFrank R. Trifari; David R. Treacy [57] ABSTRACT Ahydraulic vane motor having rotor vanes radially displaceable in slots,in which a pressure chamber is disposed in the inner part of each slot.The outer edge of a vane is pressed against a work portion of a camprofile by fluid pressure acting on the bottom of the vane. Radiallydirected flow paths along the broad sides of each vane, plus a smallcircumferential movement of the vane in the slot, provide different flowresistances on the opposite sides of the vane.

4 Claims, 7 Drawing Figures US Patent Sept. 23,1975 Sheet 1 of 23,907,467

US Patent Sept. 23,1975 Sheet 2 of2 3,907,467

Fig.2

ROTARY VANE MACHINE WITH FLUID FLOW PATHS ON EACH VANE SIDE This is acontinuation of Ser. No. 305,297, filed Nov. 10, 1972, now abandoned.

This invention relates to hydraulic machines, and more particularly tovane motors for use in position servo applications. Such a motor has astator including a stator ring provided with a cam profile, two sidemembers, and a rotor enclosed in said stator transferring the torque toan output shaft and carrying radially displaceable vanes in slots. Eachslot has a pressure chamber at its inner part. The outer edge of eachvane during the work moment of the vane is pressed against acorresponding work length of the cam profile thereby preventing pressuremedium from overflowing between the outer edges of the active vanes andthe stator ring from the high pressure to the low pressure side of thevane.

The seal between the vanes and the stator ring is a source of difficultyin machines of this type. If the motor is intended to develop hightorque at start and at low speed, which is necessary for position servopurposes, these difficulties are increased because it is then notpossible to gain an advantage from the centrifugal force on the vanes toprovide an adequate seal.

The solution to this problem is to provide a force which presses eachvane against a corresponding work length of the cam profile of thestator ring only during the work movement of the vane. It is desirablethat the resultant force directed upwards just exceeds zero, whereby thefrictional drag between vanes and stator ring and the accompanyingwearing of the vanes and the cam profile will be minimized, so the motorwill operate at the highest possible efficiency.

It is known to spring load the vanes in such a manner that they arecontinuously pressed against the cam protile. In a machine of said typethis solution means that the vanes are pressed against the cam profileby the total spring force when the vanes are inactive, and thus are notinfluenced by-an inwardly directed hydraulic force. This solution causeshigh frictional forces and consequently great wearing of the vanes andthe cam profile.

It is also known to use a hydraulic pressure derived from the highpressure side of the machine for providing an outward force. For thispurpose it is possible to use the total high pressure by feedingpressure medium from the high pressure side of the machine throughchannels into the pressure chamber in each slot, or a part of the highpressure bypassing the pressure medium through pressure reducing valvesbefore reaching the pressure chamber. The pressure in the pressurechamber acts on the inner edge of each vane to provide an outwardlydirected force. ln the first case the force on each vane during the workmovement of the vane is unsuitably great, and causes high friction andwearing. In the second case additional features are necessary to reducethe pressure, thus making the machine more complicated, which in turngives rise to greater manufacturing cost. When a vane motor is used forservo purposes the second case design is inappropriate, because the useof pressure reducing valves in the regulating process easily can giverise to oscillations in the servo system.

The invention eliminates the above mentioned drawbacks and provides bymeans of simple techniques an appropriate force action on the vanesduring the work movement. According to the invention flow paths areradially arranged along the broad sides of each vane and thecorresponding boundary surfaces of each slot, to permit a predeterminedoverflow of pressure medium from the high pressure side to the lowpressure side of the vane through the pressure chamber provided in theinner part of each slot, thereby controlling the pressure in thepressure chamber and in consequence providing an outwardly directedpredetermined force acting on each vane during its work movement.

By permitting a controlled flowing through of pressure medium from thehigh pressure side of the vane to its low pressure side a stablecondition at each vane is provided making it possible to accuratelypredetermine the action of forces on each vane.

According to the invention appropriate force action .on each vane isprovided by dimensioning the flow paths in such a manner that the flowpaths on the high pressure side and the low pressure side of said vanepresent diffferent flow resistances. The difference in flow resistancemay be provided by dimensioning the thickness of each vane and the widthof the corresponding slot such that the vane, under influence from thepressure medium, is displaced in the direction of rotation in such a waythat a gap is still provided between the vane and the low pressure sideboundary surface of the slot when the vane is pressed against saidboundary surface.

If the machine is to be used for position servo purposes the motornecessarily must be able to work reversibly i.e., in both directions ofrotation. In accordance with the invention this is achieved simply byconstructing each vane and the corresponding slot in an essentiallysymmetrical manner with respect to a plane through the machine axle andthrough the center of said slot, hereinafter referred to as the radialplane. Upon reversing the motor, the vanes are brought into contact withthe opposite boundary surfaces of the corresponding slots which meansthat the greater and smaller flow resistances change sides.

According to the invention it is also advantageous to shape the vanessuch that the ratio between the total radial length of each vane and thecorresponding length of that portion of the vane which protrudes fromthe slot is such that the mean part of the surface area of the lowpressure side of said vane situated in the slot is brought into contactwith a corresponding surface area of the boundary surface of the slotwhen said vane is pressed against the boundary surface.

According to one embodiment of the invention the broad sides of eachvane are essentially plane parallel as are the corresponding boundarysurfaces of the associated slot, and the flow paths are provided byrecessing plane parallel grooves in a radial direction in each of thebroad sides. The outer edge of each vane is straight in the axialdirection and provided with a longitudinal rounding off.

According to another embodiment of the invention the flow paths areprovided by distance means on the broad sides of the vanes and/or thecorresponding boundary surfaces of the slots, or by recessings in saidbroad sides and/or said boundary surfaces.

The invention will be more fully described in connection with apreferred embodiment of a reversible vane motor according to theinvention, having reference to the drawings, in which:

FIG. 1 is a sectional view of one side of a motor with one of the sidemembers eliminated;

FIG. 2 shows schematically a sectional view along the shaft and a radialplane of said shaft; and

FIGS. 3a, 3b, 3c, 3d and 3e are different views of a vane according tothe invention.

Referring to FIG. 1, a sectional view is shown of a motor along thedirection of the shaft. The shaft 1 is fastened to the rotor 2. Alongits periphery the rotor 2 is provided with radial slots at the edge 3,each of which slots closest to the shaft terminating in a pressurechamber 4. The slots 3 and the pressure chambers 4 extend straightthrough the rotor in an axial direction (FIG. 2). A vane 5 is providedin each of said slots 3. The vanes 5 are in contact with the cam profile7 shaped in the stator ring 6. A number of work chambers 8 aredistributed along the circumference of the stator ring 6 between the camprofile 7 and the rotor 2. Each of the work chambers 8 is coupled to achannel for feeding of and a channel for removal of pressure medium. Ifthe direction of rotation is the direction shown by the arrow thenpressure medium from the high pressure side of the machine is fedthrough the channel 9 to the work chambers 8 respectively. This feedingis carried out through communication channels from channel 9 to thefront part of the work chambers 8 respectively through a number ofgrooves in the stator ring 6 formed by recesses beside each other alongthe axial width of the stator ring and having a shape shown by thedotted lines 10. Removal of pressure medium is carried out throughidentical grooves 11 provided in the back part of each work chamber,said grooves communicating with a channel which corresponds to channel9.

The cam profile 7 of the stator ring is composed of sets of identicalprofile parts a-e, the number of which sets corresponds to the number ofwork chambers 8. Parts a-e are in turn composed of several portions,namely: the rest portion a-b at which each vane 5 is in an insertedposition and performs no work; the project portion b-c at which eachvane 5 is successively projected to its work position; the work portionc-d at which each vane is in the work position and performs useful work;the insert portion d-e at which each vane is successively inserted toits rest position.

During the time each vane 5 runs over the project portion bc the outeredge 19 of the vane (FIG. 3) is acted upon by pressure medium from thehigh pressure side, which causes a force acting on said vane in aninward radial direction, tending to insert said vane in thecorresponding slot 3. For compensation of this force and for instantfeeding of the volume of pressure medium which is required forprojection of each vane 5, the corresponding pressure chamber 4 duringthis moment is in communication with the high pressure side of themachine through a channel 12 in one of the side members which channelcommunicates the channel 9 is tangent to a broad side of a vane 5. Thefigure also shows that the bottom of each pressure chamber 4 is providedwith two radially directed holes for the compression springs 14.

The shape of the vane 5 is obvious from FIG. 3, which shows that saidvane 5 on the whole is symmetrically shaped with exception for the outeredge 19 which in opposition to the inner edge 18 shows a longitudinalround off. The inner edge of said vane 18 is completely flat. Each ofthe two broad sides 15 and 16 contains two grooves 17, the depths ofwhich are exaggerated in the drawing.

In operation of the motor, a pressure medium, usually oil of anyadequate quality, is fed to each work chamber 8 from the high pressureside of the machine through a channel, such as the channel 9; in each ofthe work chambers 8 the pressure medium is caught by those vanes 5 whichare in work position, so that said vanes 5 are exposed on the one broadside to the high pressure and on the other broad side to the lowpressure. The difference in pressures gives rise to a force acting onsaid vanes in work position so that said vanes are displaced in thedirection of rotation and bring with them the rotor 2, transferring thetorque to the shaft 1. When said vanes 5, respectively, reach the end ofthe work portions, a next set of vanes 5 have already reached therespective work positions and then take over the work movement.Thereafter the process is repeated in the manner described.

When a vane 5 passes point c on its profile portion a-e thecommunication between the channel 12 and the pressure chamber 4 isbroken. This means that the pressure in the pressure chamber decreasesrapidly because of leakage, for example between the rotor 2 and the sidemembers, which in turn means that the vane 5 is no longerhydrostatically balanced. From this it follows that the vane at thismoment is no longer acted upon by any outwardly directed force. Theproportionately weak action of the compression springs 14 may in thisconnection be disregarded. For the vane to continue to be in contactwith the cam profile 7 an outwardly directly force greater than theinwardly directed force is required.

According to the invention said outwardly directed force is provided bypermitting passage of pressure medium from the high pressure side of thevane through grooves 17 in the vane (FIG. 3) and through the workchamber 4 to the low pressure side of said vane. The pressure in thepressure chamber 4 amounts to a value between the pressure values on thehigh pressure and the low pressure side of the vane in dependence on thesizes of the flow paths.

Assuming that the pressure on the high pressure side of the vane is P,,the pressure on the low pressure side of the vane is P the pressure inthe pressure chamber P and the cross-section of the vane in thedirection of the shaft is Y, as a consequence of the symmetrical shapeof the rounded off outer edge of the vane 19 that said vane is actedupon by an inwardly directed force r (P +P )'Y and the outwardlydirected force P -Y.

From this follows that the condition for hydrostatic balancing of thevane is P V2 (P,+P which is satisfied when the flow resistance betweenthe high pressure side and pressure chamber equals the flow resistancebetween the pressure chamber and low pressure side, if leakage isdisregarded.

In practice it turns out that the vanes 5 under their movements in andout in the corresponding slots 3 are acted upon by frictional forceswhich are not completely predictable, and it also appears thatconsideration must be given to leakage; e.g., between the rotor and theside members. Therefor it is necessary to provide a flow of pressuremedium to the pressure chamber to such an extent that these factors arecompensated and that in addition some excess of outwardly directedhydraulic force is obtained to ensure sealing between the vane and thecam profile. This excess force should have a value such that the wear ofthe vanes and cam profile is minimized.

Consequently in the pressure chamber 4 a pressure is desired whichsatisfies the condition A (P,+P P P,. According to the invention thisrelationship is satisfied by dimensioning the flow paths to and from thepressure chamber in such manner that the required difference in flowresistance is obtained.

The requirement on reversibility, i.e. that the machine shall be able towork with the dame efficiency in both directions of rotation, isachieved in this embodiment of the invention by means of the completelysymmetrical shaping of the vanes 5, the slots 3 and the cam profile 7,and the feeding and removal channels for the pressure medium.

The mentioned necessary difference in flow resistance of the flow pathsto and from the pressure chambers 4 is provided by dimensioning of thethickness of the vanes (T, FIG. 3) relative to the widths of the slots(B, FIG. 1) such that each vane in the work position is displaced in thedirection of rotation. This displacement causes the flow path on thehigh pressure side of the vane to be increased by the gap formed betweenthe broad side of the vane and the corresponding boundary surface on theslot. Furthermore, because the portion of each vane which protrudes intothe work chamber has a ratio to the total radial length of said vanesuch that said vane will be displaced with its broad side parallel tosaid slot, so that one of the broad sides of said vane lies close to acorresponding boundary surface of said slot, a change in flow resistanceis achieved which will always be of a predetermined magnitude.

The flow of pressure medium from the high pressure side through thepressure chambers to the low pressure side which follows from theshaping of the vane has been shown to bring about very stable pressureconditions in the pressure chambers. The flow is, of course, kept belowa value such that it will influence the torque delivered by the motor.The flow resistance of a column can be shown to be reciprocallyproportional to the third power of the height of the column. This meansthat the dimensions of the grooves 17 and of the column which is formedby the displacement of the vane are of the order of magnitude of somehundredths of a millimeter, which in turn gives an indication of theamount of said flow.

The simple and totally symmetrical shaping of the vanes andcorresponding slots means that the manufacturing can be carried out byknown techiques at low cost. A further advantage is that thelow numberof movable parts simplifies assembly and disassembly of the motor.Endurance tests of a motor according to the described embodiment hasshown very good operating properties.

What is claimed is:

1. A reversible direction hydraulic machine comprising a stator and arotor, said stator having a cam profile defining work chambers, saidrotor connected to a shaft and enclosed within said stator, said rotorhaving a plurality of radially extending symmetrical slots spacedthereabout and a respective pressure chamber located radially inwardfrom each slot and communicating therewith, said rotor also comprising aradially displaceable vane carried in each of said slots, each vanebeing symmetrical with respect to a radial plane and having two narrowsides transverse to said plane and two broad sides, a portion of saidvane protruding from said slot for contact with said cam profile so asto prevent a working medium from flowing between an outer edge of saidvane and said cam profile from a high pressure side of the vane to a lowpressure side, said rotor having at least one flow path meanssymmetrically arranged about each broad side of each vane for permittingsaid working. medium to flow between the work chamber and the respectivepressure chamber, each vane having a thickness slightly less than thewidth of the respective slot, said flow path means being in addition tospace between said vane and said slot due to said lesser thickness ofthe vane has been inserted after the comma. said slot having a depth andsaid vane having a total radial length such that the broad side of saidvane on the low pressure side is brought into area contact with acorresponding side of said slot without tilting of said vane, whereby atotal flow path between the work chamber and the pressure chamber on thehigh pressure side of said vane has a flow resistance less than that onthe low pressure side of said vane, and upon reversal of the machine theopposite broad side of said vane will become the low pressure side andbe in area contact with a corresponding side of the slot.

2. A hydraulic machine as claimed in claim 1 wherein said flow pathmeans comprises a passage region provided between each broad side ofsaid vane and a corresponding side of said slot.

3. A hydraulic machine as claimed in claim 1 wherein said flow pathmeans comprise a recess in each broad side of each vane.

4. A hydraulic machine as claimed in claim 3 wherein said broad sides ofeach of said vanes are substantially plane parallel sides, said recessesare radially extending parallel grooves, the outer edge of each vanebeing axially straight and transversely rounded, and wherein the sidesof each slot corresponding to said broad sides are plane parallel sides.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTIONPATENT NO. 3907467 DATED September 23, 1975 INVENTOR(S) ULF CHRISTEREKENBERG ET AL It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 3, line 10, "slots at the edge 3" should be --slots 3 Column 3,line 11, "slots closest should be -slots at the edge closest-- Claim 1,lines 24 and 25, delete "has been inserted after the comma Signed andSalad this twenty-third Day of March 1976 [SEAL] A ttes t:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner oflarenlsand Trademarks

1. A reversible direction hydraulic machine comprising a stator and a rotor, said stator having a cam profile defining work chambers, said rotor connected to a shaft and enclosed within said stator, said rotor having a plurality of radially extending symmetrical slots spaced thereabout and a respective pressure chamber located radially inward from each slot and communicating therewith, said rotor also comprising a radially displaceable vane carried in each of said slots, each vane being symmetrical with respect to a radial plane and having two narrow sides transverse to said plane and two broad sides, a portion of said vane protruding from said slot for contact with said cam profile so as to prevent a working medium from flowing between an outer edge of said vane and said cam profile from a high pressure side of the vane to a low pressure side, said rotor having at least one flow path means symmetrically arranged about each broad side of each vane for permitting said working medium to flow between the work chamber and the respective pressure chamber, each vane having a thickness slightly less than the width of the respective slot, said flow path means being in addition to space between said vane and said slot due to said lesser thickness of the vanehas been inserted after the comma. said slot having a depth and said vane having a total radial length such that the broad side of said vane on the low pressure side is brought into area contact with a corresponding side of said slot without tilting of said vane, whereby a total flow path between the work chamber and the pressure chamber on the high pressure side of said vane has a flow resistance less than that on the low pressure side of said vane, and upon reversal of the machine the opposite broad side of said vane will become the low pressure side and be in area contact with a corresponding side of the slot.
 2. A hydraulic machine as claimed in claim 1 wherein said flow path means comprises a passage region provided between each broad side of said vane and a corresponding side of said slot.
 3. A hydraulic machine as claimed in claim 1 wherein said flow path means comprise a recess in each broad side of each vane.
 4. A hydraulic machine as claimed in claim 3 wherein said broad sides of each of said vanes are substantially plane parallel sides, said recesses are radially extending parallel grooves, the outer edge of each vane being axially straight and transversely rounded, and wherein the sides of each slot corresponding to said broad sides are plane parallel sides. 